CCS & IGCC, CHP, AD, and DH – clean energy technologies used in combination with syngas
If gasification was used in conjunction with carbon capture and storage (CCS), or a low carbon technology like integrated gasification combined cycle (IGCC); or when syngas is created using biomass, the technology is certainly “greener” than just burning a fossil fuel. IGCC is a fairly new technology that uses a gasifier in converting organic raw material (lignite, biomass, etc…) into syngas.
Gasification technologies to produce energy are particularly effective when used along with combined heat and power (CHP, cogeneration), anaerobic digestion (AD), and district heating (DH). These are technologies that use the syngas created through gasification, natural gas, other renewable (and non-renewable) energy sources; or these technologies are used to create even more renewable energy than just energy created during the cogeneration, AD, or district heating processes.
Creating bio-syngas with biomass by gasification
The energy created with gasification technologies is only renewable energy when the fuel source for gasification is biomass or municipal waste. Since biomass energy production, or waste-to-energy (discussed below) still involves a significant level of greenhouse gas emissions, it can’t be described as a truly “green” or “clean” technology. However, municipal waste is renewable, so waste-to-energy is a renewable energy technology. The syngas created in the waste-to-energy process, or any of the other gasification energy generating processes described below, is energy that can be used in municipal energy grids, to heat homes, or can be converted into liquefied natural gas (LNG) or compressed natural gas (CNG) for use in the transportation sector.
A significantly more environmentally friendly, cost-effective and efficient, version of gasification than coal use, is available in biomass and waste-to-energy. Biomass gasification uses feedstocks like: agricultural residues (such as wheat and straw), energy crops (like switchgrass), forestry residues and urban wood waste (for example, from construction sites). Agricultural waste, along with other waste, can also be used in the gasification process. The resulting product is known as bio-syngas (bio-SNG).
Waste-to-energy is the least complex situation in which gasification is used to create renewable energy. Waste-to-energy refers to a viable current technique for producing syngas through gasification technologies. Incineration in combination with gasification uses municipal waste as a fuel; combustion of it forms methane, CO2, and other gases, which can be captured and processed into SNG. In a waste-to-energy plant that uses incineration, these hot gases are used to make steam, which is then used to generate electricity. As the process also creates heat, which might otherwise just be waste heat, waste-to-energy is also ideal to be used in CHP plants, and for district heating. Gasification converts municipal waste to a usable synthesic gas, or syngas. Incineration of municipal solid waste has been practiced for almost 150 years as a technique to produce energy, and reduce landfill waste.
The reality is that the creation of synthetic natural gas (syngas- SNG) is a technology based on coal gasification for the majority of power plants that use gasification technologies worldwide; although it can also use municipal waste, other biomass, petroleum, or natural gas, as the primary feedstock. Gasification uses fossil fuels or organic based carbon materials to create the gases which make up syngas (by combining the feedstock and oxygen at extremely high temperature, after which the gas undergoes a clean-up process).
Lignite, a brownish type of coal, is the type of coal often used as a fuel source in the process of creating syngas in much of the world. Gasification uses the coal (or other feedstock), along with steam and oxygen, to create syngas. The syngas goes through a clean-up process (methanation); and can then be burned directly to generate electricity and/ or heat for homes and businesses; or the syngas can be processed to create products including methanol, nitrogen-based fertilizers, other chemicals and compounded materials, or hydrogen, for oil refining and transportation fuels. Coal gasification, especially integrated gasification combined cycle, is sometimes called a “clean coal” technology because it can create energy with less harm to the environment than traditional fossil fuel use.
The leading region in the world for syngas production is Asia, in particular China. China mostly uses coal for its syngas production, relying on their vast coal deposits, thus still producing significant quantities of greenhouse gas emissions. China is trying to rely more on domestic sources for gas and less on importing liquefied natural gas. A large number of gasification plants are also found in India, South Korea, Taiwan, and Singapore.
The Africa/ Middle East regions also produce a significant quantity of syngas, more than Europe, or the United States. However, production of syngas in Europe uses a wider selection of feedstocks, technologies and products than other regions. The coal-based units in Europe primarily utilize IGCC technologies.
A fairly new gasification plant in Swindon, England illustrates the advancements that European nations are making with gasification. Methanation is used to transform gasified biomass into grid-quality syngas in the Swindon plant, the biosynthetic natural gas (bio-SNG) then providing power to the grid.
Most syngas production in North America lies within the United States. These plants include: natural gas facilities that primarily produce chemicals, and coal and petroleum based plants that produce either power, chemicals and fertilizers or syngas, including a couple of IGCC plants. In Canada, gasification is also used to produce hydrogen and power to upgrade synthetic crude oil from the tar sands.
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